1. Field of the Invention
The present invention relates to an ophthalmic apparatus to be used in ophthalmological clinics and others.
2. Description of Related Art
In some conventional cases, alignment (positioning) of an ophthalmic apparatus with respect to an eye to be examined is usually performed based on observation of a luminescent spot image (a reflex) formed on the center of a cornea of the examinee""s eye by alignment, light projected thereon and an aiming mark. In other cases, instead of using the corneal center luminescent spot image, alignment is performed based on observation of a Mayer ring image or the shape of a pupil.
However, a conventional apparatus using the corneal center luminescent spot image has a problem that if the alignment light which forms the luminescent spot image on the corneal center is small in luminous flux width, the luminescent spot image formed on the cornea could not be visually observed until the alignment is adjusted up to a point, causing difficulty in completing the alignment. Alternatively, an ophthalmic measurement apparatus using the luminescent spot image for alignment also has the following disadvantage. When light sources for alignment are turned off in order to prevent alignment light from interfering measurement as noise light, misalignment could not be detected during the measurement.
On the other hand, the latter apparatus performing alignment with reference to the center of the Mayer ring image or the pupil center has a problem of difficulty in centering because the Mayer ring image and the pupil have no specific center to be aimed.
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide an ophthalmic apparatus enabling easy alignment with respect to an eye to be examined.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the purpose of the invention, there is provided an ophthalmic apparatus provided with an ophthalmic unit for examination, measurement, or treatment, the unit having a center axis which is aligned with respect to an examinee""s eye, the apparatus including: observation means through which an image of an anterior part of the examinee""s eye is observed; position detection means which projects light to the examinee""s eye and detects reflection light from the examinee""s eye to obtain a position of a center of a cornea or a pupil of the examinee""s eye; and display means which displays a graphic mark showing the corneal center or the pupil center with an aiming mark based on a detection result by the position detection means, the marks being superimposed on the anterior part image formed by the observation means.
According to another aspect of the present invention, there is provided an ophthalmic apparatus provided with an ophthalmic unit for examination, measurement, or treatment, the unit having a center axis which is aligned with respect to an examinee""s eye, the apparatus including: observation means through which an image of an anterior part of the examinee""s eye is observed, the observation means which includes a photographing optical system which photographs the anterior part and a display which displays the photographed anterior part image; position detection means which obtains a position of a center of a cornea of the examinee""s eye, the position detection means which includes an index projection optical system which projects a first alignment index close to an optical axis of the photographing optical system and a second alignment index far from the optical axis of the photographing optical system onto the cornea of the examinee""s eye, and an index detection optical system provided with a photoelectric detecting element which detects cornea reflection images of the first and second alignment indexes; and misalignment detection means which detects an apex of the cornea of the examinee""s eye based on a detection result by the index detection optical system to obtain misalignment, wherein the index projection optical system projects only the second index during measurement, and the misalignment detection means obtains misalignment during measurement based on a result of detection of an image of the second index.
According to another aspect of the present invention, there is provided an ophthalmic apparatus provided with a measurement unit having a measurement optical system, the measurement optical system having a measurement optical axis which is aligned with respect to an examinee""s eye, the apparatus including: position detection means which obtains a position of a center of a cornea of the examinee""s eye, the position detection means which includes an index projection optical system which projects a first alignment index close to the measurement optical axis and a second alignment index far from the measurement optical axis onto the cornea of the examinee""s eye, and an index detection optical system provided with a photoelectric detecting element which detects cornea reflection images of the first and second alignment indexes; and misalignment detection means which detects an apex of the cornea of the examinee""s eye based on a detection result by the index detection optical system to obtain misalignment, wherein the index projection optical system projects only the second index during measurement, and the misalignment detection means obtains misalignment during measurement based on a result of detection of an image of the second index.